Recovering R-123 from a Centrifugal Chiller
A 400-ton centrifugal chiller uses R-123, a low-pressure refrigerant, and has a nameplate charge of 650 lb. The chiller operates with the evaporator normally in a vacuum. A gasket leak requires opening the chiller. The technician has a high-pressure recovery machine and a low-pressure recovery machine. The facility manager asks if they can use the high-pressure machine because it is faster and if they can vent the remaining R-123 because it is a “low-pressure” refrigerant and the amount is large. The technician must recover the refrigerant, repair the gasket, and evacuate. The technician is certified Type III. The chiller uses a purge unit. The manager wants to minimize downtime. The technician must decide which recovery equipment to use, what evacuation level to reach, and what records to keep. R-123 is an HCFC.
1. Which recovery machine is appropriate for R-123, and why?
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The low-pressure recovery machine is appropriate. R-123 has a low vapor pressure, and a high-pressure recovery machine may not be able to pull the system down to the required vacuum without cavitation or overheating. Low-pressure recovery equipment is designed with larger displacement and appropriate controls to handle low-pressure refrigerant and to reach 25 inches of mercury vacuum. Using the wrong machine could leave refrigerant in the system and increase the risk of venting. The technician must also use a recovery cylinder rated for R-123 and follow the 80% fill rule.
2. What evacuation level must be achieved for a low-pressure appliance, and how does it differ from a high-pressure appliance?
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For a low-pressure appliance, the required evacuation level is 25 inches of mercury vacuum, not 500 microns. Low-pressure chillers cannot be evacuated to the same micron level as high-pressure systems without special equipment, and the regulation sets the 25 in Hg standard. The technician should use a low-pressure vacuum pump or recovery machine capable of reaching that level and should hold the vacuum to verify no leaks. For high-pressure appliances, the target is 500 microns. Confusing the two standards could result in improper evacuation.
3. What are the venting and recordkeeping requirements for this job?
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R-123 is an HCFC and is subject to the Section 608 venting prohibition, so the technician must not vent it. The technician must recover the refrigerant before opening the chiller, record the amount recovered and the amount recharged, and keep service records. Because the charge is 650 lb, leak-repair rules may apply if the leak rate exceeds the applicable threshold; the technician should calculate the leak rate and document it. The technician must be Type III certified to service low-pressure appliances. The facility manager cannot authorize venting. The purge unit should be operated according to the manufacturer’s instructions to minimize refrigerant loss.